Electromyography (EMG) is a neurophysiological diagnostic procedure to assess the health of muscles and the nerves.
There are two components to an EMG test: the nerve conduction studies (neurography) and needle EMG (myography).
- Nerve conduction study is performed to evaluate nerve function by electrical stimulation of a peripheral nerve and recording potentials by surface electrodes at the specific sites. It is relevant for diagnostics to consider nerve conduction velocity as well as shape and amplitude of the registered potential.
- Needle EMG is performed to evaluate electrical activity of muscle fibers by inserting fine needle electrode into a certain muscle and recording potentials at rest and when a muscle is slightly contracted. It is relevant for diagnostics to consider audiovisual characteristics of the potentials (sound, shape, size), provoking moments etc.
Depending on diagnostic targets the test may involve both nerve conduction studies and needle EMG or nerve conduction studies only.
Electromyography is performed to help diagnose or rule out a number of conditions:
- Muscle disorders, such as muscular dystrophy or polymyositis;
- Diseases affecting the connection between the nerve and the muscle, such as myasthenia gravis;
- Disorders of peripheral nerves, such as carpal tunnel syndrome, peripheral neuropathies, traumatic nerve injury;
- Disorders that affect the nerve root, such as cervical and lumbal radiculopathy;
- Disorders that affect the motor neurons, such as amyotrophic lateral sclerosis or polio.
The procedure should take between 20 and 60 minutes depending on the issue to be clarified. Avoid using any creams on the day of the test. Body and skin temperature can affect the results of this test, so it is recommended to keep your arms and legs warm, especially if it is cold outside. If you are taking blood thinners or anticoagulants, have a pacemaker or any other electrical medical device, inform the doctor performing the test before it is done.